Computation of energy dependent scattering amplitudes via analytic continuation of the fredholm determinant

A rapid method for calculating partial-wave scattering amplitudes over a range of energies is presented. Approximate values of the partial-wave Fredholm determinant are computed at a number of points in the complex energy plane from a single matrix tridiagonalization and are continued to the real axis via point-wise rational fraction analytic continuation. For two model problems accurate scattering information is obtained over a wide range of energies, and resonances are easily located by noting the zeros of the real part of the determinant.